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Interest in mobile chemical sensors is on the rise, but significant challenges have restricted widespread adoption into commercial devices. To be useful these sensors need to have a predictable response, easy calibration, and be integrable with existing technology, preferably fitting on a single chip. With respect to integration, the CMOS imager makes an attractive template for an optoelectronic sensing platform. Demand for smartphones with cameras has driven down the price and size of CMOS imagers over the past decade. The low cost and accessibility of these powerful tools motivated us to print chemical sensing elements directly on the surface of the photodiode array. These printed colorimetric microdroplets are composed of a nonvolatile solvent so they remain in a uniform and homogeneous solution phase, an ideal medium for chemical interactions and optical measurements. By imaging microdroplets on the CMOS imager surface we eliminated the need for lenses, dramatically scaling down the size of the sensing platform to a single chip. We believe the technique is generalizable to many colorimetric formulations, and as an example we detected gaseous ammonia with Cu(II). Limits of detection as low as 27 ppb and sensor-to-sensor variation of less than 10% across multiple printed arrays demonstrated the high sensitivity and repeatability of this approach. Sensors generated this way could share a single calibration, greatly reducing the complexity of incorporating chemical sensors into mobile devices. Additional testing showed the sensor can be reused and has good selectivity; sensitivity and dynamic range can be tuned by controlling droplet size.

Certified reference materials (CRMs) are an essential part of the quality assurance (QA) necessary for the reliable analytical measurement of nutrients in seawater. The CRMs currently available for these analyses are not matrix matched to marine samples. QUASIMEME routinely produces test materials for the nutrients in seawater and nutrients in estuarine water and low-salinity open water Laboratory Performance Studies (LPS) that are both homogeneous and stable. QUASIMEME, in conjunction with Eurofins Scientific, Denmark have produced two reference materials (RMs). The homogeneity testing and preliminary stability studies were carried out by QUASIMEME, and the results are presented in this article. Participants of the QUASIMEME LPS who demonstrated satisfactory long-term performance for the analysis of nutrients in seawater and nutrients in estuarine water and low-salinity open water were invited to take part in the certification exercise. Twenty laboratories returned data, a summary of which is also presented. The certification and long-term stability testing and additional data analysis were carried out by Eurofins Scientific, Denmark, and are outwith the scope of this article and not reported here. Eurofins Scientific, Denmark have marketed these RMs as part of their range of VKI Reference Materials (further information is available from eurofins@eurofins.dk).

Using subsurface vertical flow constructed wetlands (SSVFCWs) with intermittent loading it is possible to fulfil the stringent Austrian effluent standards regarding nitrification. For small plants (less than 500 persons) standards for ammonia nitrogen concentration have to be met at water temperatures higher than 12 degrees C, effluent concentrations and treatment efficiencies for organic matter have to be met the whole year around. According to the Austrian design standards the required surface area for SSVFCWs treating wastewater was 5 m2 per person. Within the first part of an Austrian research project the goal was to optimise, i.e. minimise the surface area requirement of vertical flow beds. Therefore, three SSVFCWs with a surface area of 20 m2 each have been operated in parallel. The organic loads applied were 20, 27 and 40 g COD/m2/d, which corresponds to a specific surface area requirement of 4, 3 and 2 m2 per PE, respectively. The paper compares the effluent concentrations and elimination efficiencies of the three parallel operated beds. It could be shown that a specific area demand of 4 m2 per person is suitable to be included in the revision of the Austrian design standard. Additionally it could be shown that during the warmer seasons (May-October) when the temperature of the effluent is higher than 12 degrees C the specific surface area might be further reduced; even 2 m2 per person has been proven to be adequate.

Ammonia-contaminated groundwater enters the Upper Colorado River from beneath the abandoned Moab Uranium Mill Tailings Pile near Moab, Utah. This reach of the Upper Colorado River was designated as critical habitat for four endangered fish species because it is one of the few existing areas with known spawning and rearing habitats. Un-ionized ammonia (NH3) concentrations frequently exceed 1.00 mg/L in backwaters adjacent to the tailings pile, which exceeds the Utah 30-d average chronic water quality criterion for un-ionized ammonia (0.07 mg/L NH3; temperature 20 degrees C; pH 8.2) by a factor of more than 10. However, there is little published information regarding the sensitivity of endangered fishes to ammonia. We conducted 28-d static renewal studies with post-swim-up larvae to determine the relative sensitivity of Colorado pikeminnow (Ptychocheilus lucius), razorback sucker (Xyrauchen texanus), and the standard surrogate fathead minnow (Pimephales promelas) to NH3. Chronic values (ChVs) for mortality and growth were determined as the geometric mean of the no observed effect concentration and the lowest observed effect concentration based on analysis of variance. The ChVs for growth of fathead minnow, Colorado pikeminnow, and razorback sucker were 0.43, 0.40, and 0.67 mg/L NH3, respectively. The ChVs for mortality of fathead minnow, Colorado pikeminnow, and razorback sucker were 0.43, 0.70, and 0.67 mg/L NH3, respectively. Therefore, the ChVs for mortality and growth were similar for fathead minnow and razorback sucker; however, the ChV for growth was lower than the ChV for mortality for Colorado pikeminnow. Maximum likelihood regression was used to calculate 28-d lethal concentrations (LCx) for each species. The 28-d LC50, LC20, and LC1 values for fathead minnow were 0.69, 0.42, and 0.13 mg/L NH3, respectively. The 28-d LC50, LC20, and LC1 values for Colorado pikeminnow were 0.76, 0.61, and 0.38 mg/L NH3, respectively. The 28-d LC50, LC20, and LC1 values for razorback sucker were 0.54, 0.38, and 0.25 mg/L NH3, respectively. The fathead minnow, Colorado pikeminnow, and razorback sucker are relatively similar in sensitivity and rank at the 35th, 49th, and 31st percentiles, respectively, of the theoretical chronic fish sensitivity distributions for NH3. The existing water quality criteria for NH3, if met by remediation activities at the Moab site, would be protective of these endangered fishes even if fish sensitivity is based on the conservative LC1 value.

Ammonia toxicity data for freshwater mussels (Unionidae), a significantly imperiled taxa, were used to derive estimates of concentrations that would not likely be harmful in acute and chronic exposures and to assess the protectiveness of current U.S. Environmental Protection Agency (U.S. EPA) water quality criteria to this family of organisms. Thirty acute (24-96-h) median lethal concentrations (LC50s), covering 10 species in eight unionid genera, were used to calculate genus mean acute values (GMAVs) ranging from 2.56 to 8.97 mg/L total ammonia as N at pH 8. Freshwater mussels are at the sensitive end of the range when added to the GMAVs from the database used to derive the U.S. EPA criteria maximum concentration (CMC). We derived two estimates of acute exposure water quality guidance for the protection of freshwater mussels (CMC(FM)) by a recalculation of the CMC after adding freshwater mussel GMAVs to the U.S. EPA data set. The CMC(FM)s of 1.75 and 2.50 mg/L total ammonia as N at pH 8 average 60% less than the U.S. EPA CMC of 5.62 mg/L total ammonia as N at pH 8 for application when salmonids are present. These values average about 75% less than the CMC for application when salmonids are absent. No chronic ammonia exposure data existed for unionids. Thus, we applied a range of estimated acute:chronic ratios to the acute toxicity data set, expanded with the freshwater mussel GMAVs. to estimate continuous ammonia concentrations that may be protective of freshwater mussels. These estimates ranged from 0.3 to 1.0 mg/L total ammonia as N at pH 8, about 20 to 75% less than the U.S. EPA criteria continuous concentration (CCC) of 1.24 mg/L total ammonia as N at pH 8 and 25 degrees C. The current numeric criteria for ammonia may not be protective of mussels, more than half of whose nearly 300 species are in decline in North America. While the CMC(FM) and CCC(FM) are not equivalent to revised U.S. EPA criteria, they are offered as interim guidance for the protection of freshwater mussels.

The present study investigates the oxidation of methyl tert-butyl ether (MTBE) by conventional ozonation and the advanced oxidation process (AOP) ozone/hydrogen peroxide under drinking water treatment conditions. The major degradation products identified were tert-butyl formate (TBF), tert-butyl alcohol (TBA), 2-methoxy-2-methyl propionaldehyde (MMP), acetone (AC), methyl acetate (MA), hydroxyisobutyraldehyde (HiBA), and formaldehyde (FA). The rate constants of the reaction of ozone and OH radicals with MTBE were found to be 0.14 and 1.9 x 10(9) M(-1) s(-1), respectively. The rate constants for the same oxidation processes were also measured for the degradation products TBF, MMP, MA, and HiBA (k(O3-TBF) = 0.78 M(-1) s(-1); k(OH-TBF) = 7.0 x 10(8) M(-1) s(-1); k(O3-MMP) = 5 M(-1) s(-1); k(OH-MMP) = 3 x 10(9) M(-1) s(-1), k(O3-MA) = 0.09 M(-1) s(-1), k(O3-HiBA) = 5 M(-1) s(-1); k(OH-HiBA) = 3 x 10(9) M(-1) s(-1)). Since all compounds reacted slowly with molecular ozone, only the degradation pathway of MTBE with OH radicals has been determined, including the formation of primary degradation products. In experiments performed with several natural waters, the efficiency of MTBE elimination and the formation of bromate as disinfection byproduct have been measured. With a bromide level of 50 microg/L, only 35-50% of MTBE could be eliminated by the AOP O3/H2O2 without exceeding the current drinking water standard of bromate (10 microg/L). The transient concentrations of MTBE and its primary degradation products were modeled using a combination of kinetic parameters (degradation product distribution and rate constants) together with the ozone and OH radical concentration and were in good agreement with the experimental results.

Due to instability in static mixtures, in the past only dynamic preparation techniques for mixtures of NH3 and HCl were maintained; however, recent developments of new passivation techniques for cylinder treatment and commercially available nitrogen with a very low content of impurities have opened up the possibility of preparing stable mixtures in cylinders by gravimetry. Mixtures of NH3 (300 microL/L and 30 microL/L) and HCI (300 microL/L) were prepared in nitrogen in cylinders with different passivation treatments. The mixtures were compared with dynamically prepared mixtures using Photo Acoustic detection (PAS) and FT-IR. The uncertainty is about 3.5% with PAS analysis for NH3 at the 300 microL/L level. For the analysis of HCI with FT-IR the initial uncertainty in the 300 microL/L mixtures is about 7%. Two of the HCI mixtures show significant instability; for the other three mixtures the uncertainty in the measurement is too large to discriminate between stability and instability. The NH3/N2 mixtures are stable within 3.5% for a one-year period. The stability of the 30 microL/L mixtures of NH3 cannot be underpinned by measurement results, but a systematic effect in the measurement procedure seems more likely than instability. Improvement in the measurement procedure should clarify this point.

HPLC and TLC systems were sought for routine assurance of [13N]NH3 for human PET studies. An ion chromatograph with conductivity and radioactivity detection was used to confirm that [13N]NO2- and [13N]NO3- were the major 13N species formed by the 16O(p, alpha)13N reaction in a small volume (0.5 mL) water target irradiated with protons (24 MeV), and that Devarda's alloy reduction and distillation in an apparatus constructed of disposable components and requiring no external heating gave radiochemically and radionuclidically pure [13N]NH3. Merck polyethylene-backed TLC plates were developed in the upper phase of the solvent mixture: H2O/acetone/propionic acid (6:4:2, v/v) saturated with NaCl. The Rf of [13N]NH3 was 0.6. HPLC was conducted with a 25 X 0.46 cm column with 2 mL/min CH3CN/10 mM aqueous sodium 1-octanesulfonate (1:2, v/v). [13N]NH3 eluted at 3.5 min.

Twenty three UK commercially produced ammonia caramels and eight experimentally produced ammonia caramels have been analysed by a range of physical and chemical tests, which include solids content, nitrogen levels, colour intensity and pH. A statistical treatment of the results is reported.